Phase I: In the initial treatment phase (Phase 1), patients will be randomized to one of the three atypical antipsychotics or placebo in the ratio 100:100:100:150 respectively. After two weeks, the investigator can move the patient to the next phase because of lack of efficacy or tolerability. At week 12, the investigator can decide whether the current medication is sufficiently optimal or it would be more beneficial to try another randomized medication.